The present invention generally relates to a thin-walled catheter and method for making same, and more particularly, to a catheter that is thin-walled while still exhibiting excellent strength and torque response characteristics, the thin-walled construction being one in which a thin flexible outer sheath overlies a thin rigid inner sheath to thereby form the elongated tubular portion of the catheter. The catheter further includes a flexible, atraumatic tip portion located at one end of the elongated tubular member and that is a fuseless, integral extension of the flexible outer sheath that is formed at a gap between lengths of the rigid inner sheath.
Catheters such as intravascular catheters are well known for use in diagnostic and therapeutic applications wherein it is necessary to administer a fluid to, or otherwise contact, a precise location within the cardiovascular system, for example, by guiding the tip or distal end of the catheter through branching blood vessels. Such guiding is accomplished in part by manipulation of a proximal portion of the catheter in order to impart forces needed to curve and guide the catheter through the curving and branching blood vessels.
Because these types of catheters are used in an intravascular manner, they must have an extremely small outside diameter. Inasmuch as such catheters typically come into contact with living tissue, including organs such as the heart, it is extremely important that the catheter be in place for a minimal length of time. The overall insertion time includes the length of time needed to transmit the therapeutic or diagnostic fluid through the length of the catheter. This flow velocity is dependent upon the internal diameter of the catheter, as well as the strength of the catheter which limits the pressure that can be applied in order to transmit the fluid therethrough. It is also important that these catheters be very resistant to the formation of kinks therein which requires a certain degree of stiffness, while at the same time possessing adequate flexibility to be responsive to maneuvering forces and to be as atraumatic as possible.
Catheters that require a relatively stiff inner lumen can advantageously utilize these properties. Included are intravascular catheters, guiding catheters through which balloon catheters for angioplasty techniques and the like can be passed, and sheaths where wall thinness and strength are particularly important.
The present invention provides a catheter that has an elongated tubular portion having an internal layer that is a rigid layer which exhibits strength and stiffness properties that are extremely advantageous for an intravascular catheter or the like while still having adequate flexibility in its thin-walled sheath condition to permit the flexibility required of such a catheter. Closely overlying, and typically extruded onto, the rigid inner sheath is a flexible outer sheath that is compatible with the rigid inner sheath and that, as a layer over the rigid inner sheath, imparts improved atraumatic properties to the catheter and contributes to the overall flexibility of the unitary device, while also providing convenient opportunities to impart radiopaque properties to the catheter. These catheters, which are preferably produced by extrusion techniques including coextrusion when appropriate, have a flexible tip portion that is a fuseless, integral extension of the flexible outer sheath.
By this combination, it has been discovered that the advantages of a multi-walled catheter are achieved while at the same time providing a fuselessly tipped catheter that has the thin-walled properties often associated with catheters having single-layered walls, including the atraumatic and flexibility attributes normally associated therewith.
Accordingly, a general object of the present invention is to provide an improved fuselessly tipped thin-walled catheter.
Another object of the present invention is to provide a thin-walled catheter that is especially suitable for highly delicate treatments and diagnostic procedures including coronary angiography, angioplasty, ventricular and aortic flush injections, and other similar procedures within the cardiovascular system.
Another object of the present invention is to provide an improved thin-walled catheter and method of making same which utilizes a polycarbonate material as a thin-walled extrusion having flexibility suitable for intravascular catheters and the like, while still retaining its highly advantageous strength properties.
Another object of this invention is an improved method for forming a thin-walled catheter which includes fuselessly forming a tip portion that is integral with an outer flexible sheath and that is extruded over a gap in an inner rigid sheath.
Another object of the present invention is to provide an improved thin-walled catheter that has an inner layer and an outer layer of extruded material and that does not require adding any strands of strengthening material therebetween. Another object of the present invention is the utilization of a polycarbonate material in a thin-walled form within the elongated tubular member of a catheter such as an intravascular catheter.
Another object of the present invention is to provide an improved intravenous catheter and method of producing same with a flexible, atraumatic fuselesstip that has high visibility under flouroscopy.
Another object of the present invention is to provided an improved intravascular catheter that exhibits excellent torque response or control and that is particularly resistant to kinking, while still possessing the atraumatic properties needed for an intravascular catheter.
These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detailed description.